I am doing some prototyping with the new Xbee3 Global Cat-m/NB-IoT, GM2 model and running into a minor problem. Just for clarification, this is the higher power variant with the optional 2G fallback. My low power version are running like champs.
One of our products runs off battery using NiMH batteries and our packs are basically three cells in series to produce a nominal voltage of 3.6V (1.2V x 3 = 3.6V, full charge puts it just north of 4.0V). The problem I am running into is that when the battery drops to about 3.5V, the XBee will not connect to the cellular network. I am assuming that as the modem searches for signal, there is an inrush demand which is not being met in my configuration. Especially if its demanding more power for areas with low signal quality.
I was hoping someone out there had a setup that worked well. I did follow the recommendations for caps in the documentation in section: Hardware > Design Recommendations > Minimum Connection Diagram. I had no luck with this as well as a few other test configurations. However, I don’t see any indication for which XB3 variant these recommendations are for. I will note that I was prototyping with thru-hole ceramic caps that probably aren’t the best quality and materials, but I figured they’d get me close for a final design.
I am thinking…probably just making a dumb mistake which is typical for me. I am also wondering if the demand of this XB3 model is just going to be too much for a simple battery setup. On one of our other products, I run a 12VDC system and use a quality switching voltage regulator setup and those are working great. I am thinking I might just have to make this version 12V based due to the additional power requirements. No the end of the world, I am just in the pursuit of keeping everything as simple as possible.